Security is a concern for any device that is connected to a public network, such as the Internet. Viruses, worms, Trojan horses, identity theft, software piracy, malicious attacks, and extortion using threats of data destruction are widespread. An operating system can provide numerous security features to guard against such attacks. However, the security features of an operating system are ineffective if the operating system itself has been corrupted, infected, or the victim of a malicious attack.